GIFT   OF 


The  Problem  of  Rocky  Mountain 
Spotted  Fever 


BY 


,VVi  • 


n^^7 


P.  A.  Surgeon  W.  C.  Rucker 

United  States  Public  Health 

and 

Marine-Hospital  Service 


REPRINT  FROM 

U/te  MILrlTA^RY  SVRGKON 


WASHINGTON.    D.   C. 

THE    ASSOCIATION    OF    MILITARY   SURGEONS 

1911 


The  Problem  of  Rocky  Mountain 
Spotted  Fever 


BY 


P.  A.  Surgeon  W.  C.  Rucker 

United  States  Public  Health 

and 

Marine-Hospital  Service 


REPRINT  FROM 

^he  MILrlTARY  SVRGEON 


WASHINGTON,    D.   C. 
THE    ASSOCIATION    OF    MILITARY   SURGEONS 

1911 


.A-^ 


V 


t^^ 


THE    PROBLEM    OF    ROCKY    MOUNTAIN    SPOTTED 

FEVER.* 

By  p.  a.  Surgeon  W.  C.  Rucker,  U.  S.  Public  He;alth  and 
Marinh-Hospital  Service. 

HISTORY. 

FOR  over  a  decade  Rocky  Mountain  spotted  fever  has  been  a 
problem  of  great  interest  to  the  physician,  the  zoologist 
and  the  sanitarian.  Its  geographic  limitation,  seasonal  prevalence, 
intimate  association  with  wood-ticks  and  variation  in  severity  in 
different  localities,  combine  to  make  it  one  of  the  most  interest- 
ing and  intricate  disease  problems  which  has  arisen  in  our  genera- 
tion. It  has  a  peculiar  interest  for  us  because  apparently  it  i§  con- 
fined to  the  American  continent.  Some  of  the  earlier  investiga- 
tive work  in  this  field  was  done  by  members  of  the  Association  of 
Military  Surgeons  of  the  United  States,  and  it  has  therefore  been 
considered  appropriate  to  present  a  brief  review  of  the  progress  in 
the  study  of  the  disease  to  the  Association  and  to  indicate  the  lines 
along  which  investigative  and  eradicative  work  should  be  carried 
in  the  future. 

Although  the  disease  has  been  known  in  Idaho  and  Montana 
since  1873,  the  first  specific  reference  to  it  in  literature  is  to  be 
found  in  the  report  of  the  Surgeon  General  of  the  Army  for  the 
fiscal  year  ending  June  30,  1896  (76).  It  is  there  stated  that  "the 
Surgeonf  at  Boise  Barracks  referred  in  one  of  his  monthly  re- 
ports to  the  prevalence  of  spotted  fever  in  the  civil  settlements  in 
the  neighborhood  of  the  post.  On  being  requested  to  give  fuller 
particulars  concerning  this  fever,  he  stated  that  as  he  had  not 
seen  any  of  the  cases  that  occurred  he  had  called  upon  his  medi- 
cal friends  in  civil  life  for  information,"    These  gentlemen  (Drs. 


•Read  by  title  at  the  20th  Annual  Meeting. 

tThen  Captain,  now  Lt.  Col.,  Deputy  Surg.  Gen'l,  Rtd.,  Marshall  W.  Wood,  M.  C, 
U.  S.  A. 


244501 


4  P.  A.  SURGEON  W.  C.  RUCKER. 

C.  L.  Sweet,  W.  D.  Springer,  R.  M.  Fairchild,  L.  C.  Bowers,  J. 
K.  Dubois,  D.  W.  Figgins  and  H.  Zipf )  responded  promptly  and 
their  reports  constitute  the  first  published  accounts  of  Rocky 
Mountain  spotted  fever  as  a  disease  entity. 

It  was  not  until  1899,  however,  when  Dr.  E.  E.  Maxey  of  Boise, 
Idaho,  read  a  paper  entitled,  "Some  observations  on  the  so-called 
spotted  fever  of  Idaho,"  (32)  before  the  Oregon  State  Medical 
Society,  that  the  disease  began  to  attract  any  wide-spread  atten- 
tion. This  lucid  paper  expresses  the  opinion  that  spotted  fever 
is  a  specific  disease  and  gives  an  accurate  description  of  its  clini- 
cal manifestations. 

In  1902,  the  then  newly  organized  Montana  State  Board  of 
Health  selected  for  its  first  task  the  careful  investigation  of  the 
disease,  securing  for  this  purpose  the  services  of  Drs.  L.  B.  Wil- 
son and  W.  M.  Chowning  of  the  University  of  Minnesota.  Their 
work,  which  was  done  in  the  Bitter  Root  Valley  of  Montana,  con- 
stitutes the  first  serious  laboratory  study  of  the  disease  (12,  72, 
72)y  74.  75).  afid  in  a  paper  written  July  i,  1902,  (69)  they  sug-' 
gested  the  role  of  the  ground  squirrel  (Citellus  columbianus) 
and  the  tick  {Dermacentor  andersoni)  as  host  and  vehicle  of 
transmission,  respectively.  In  the  same  year  Surgeon  J.  O.  Cobb 
of  the  U.  S.  Public  Health  and  Marine-Hospital  Service,  visited 
the  Bitter  Root  Valley  and  wrote  a  description  of  the  disease  (13). 
Subsequent  investigations  have  been  made  by  Ashburn  (5,  6,  7), 
Craig  (7,  16),  and  Keiffer  (26),  of  the  Army;  Anderson  (i,  2, 
3),  Stiles  (64-70,  inclusive),  Francis,  King  {2y),  and  McClintic 
of  the  Public  Health  and  Marine-Hospital  Service;  and  by  sev- 
eral others,  the  most  noteworthy  among  whom  are  the  martyred 
Ricketts  (41-54,  inclusive),  and  his  associates. 

GEOGRAPHIC  DISTRIBUTION. 

The  disease  has  been  reported  from  nearly  all  the  states  in  the 
Rocky  Mountain  group,  California,  Colorado,  Idaho,  Montana, 
Nevada,  Oregon,  Utah,  Washington  and  Wyoming  each  having 
foci.  Cases  have  also  been  reported  from  the  District  of  Alaska. 
The  geographic  distribution  of  the  disease  is  shown  as  follows  in 
tabular  form : 


ROCKY  MOUNTAIN  SPOTTIW  fliVUR. 
Geographic  Distribution  of  Rocky  Mountain  Spotted  Fever. 


State. 


Alaska  . . 
California 
Colorado 

Idaho  

Montana 


Nevada   . . . 

Oregon 

Utah   

Washington 
Wyoming  . . 


Locality. 


Klondike    . 

Calneva  . . . 

Carbondale 
Rifle  


Valleys  of  the  Weiser, 
Payette,  Boise  and 
Wood  Rivers :  North 
bank  of  the  Snake 
River :  Southwestern 
Idaho 

West  side   Bitter  Root 

Valley. 

Phillipsburg,  Clinton, 
Camas  Prairie 

Rock  Creek,  Blackfoot, 
Rattlesnake  and  Lolo 
Valleys 

Bridger  

Livingston ■. 

Quinn  River  Valley 

Paradise  Valley,  Win- 
nemucca.  Ft.  McDer- 
mitt,  Reno 

Burns    

Lakeview  

Merrill   

Cedar  Valley,  Fairfield, 

Cedarfort 

Heber  City 

Moses  Lakes,  Douglas 
Co 

Thermopolis,  Meyers- 
ville,  Shoshone  River. 

Crow  Creek  

South  Pass,  Ft.  Fetter- 
man,  Ft.  Steele,  Chey- 
enne  

Cody,  Meeteese 


Reporter. 


Gwinn  (21). 

Snow.* 

Braden  (56). 
Le  Rosignol  and 
Hotopp  (56). 


Maxey  (32). 

Wilson    (72)    and 
Chowning. 
Anderson  (i). 
Stiles  (64). 

Andersofi   (2). 


McCullough  (36). 
Gates  (2,  66). 
Alton  (64). 

Kendall   (2). 


Robinson  (56) 

lieary  (19)". 
Steiner    (56). 
Patterson   (56). 

Noves   (56). 
Wheritt  (56). 

Smith   (61). 


Gates   (2,  66). 
Kieffer  (26). 


Robinson   (56). 
Bradbury  (75). 


•Personal  letter. 


6  P.  A.  SURGEON  IV.  C.  RUCKER. 

Data  regarding  the  prevalence  of  Rocky  Mountain  spotted 
fever  in  the  known  infected  IccaHties  is  very  sparse  except  in 
Montana  and  Idaho.  In  the  latter  state,  Dr.  Edward  K.  Maxey 
of  Boise,  collected  data  on  380  cases  which  occurred  during  1908. 
The  following  table  shows  the  occurrence  of  the  disease  in  the 
Bitter  Root  Valley  from  1885  to  191 1,  inclusive,  representing  data 
collected  by  Wilson  and  Chowning,  Anderson,  Stiles  and  Mc- 
Clintic: 

Human   Cases   of  Rocky   Mountain   Sj>otted  Fever   in   the   Bitter  Root 
Valley  of  Montana. 


Year. 

Cases. 

Deaths. 

Mortality. 

Year. 

Cases. 

Deaths. 

Mortality. 

Per  Cent. 

Fer  Cent 

1885 

1 

1 

100 

1899    _, 

23 

14 

60.8 

1886 

1 

1 

100 

1900    — 

12 

9 

75 

1887 

0 

0 

0 

1901  -, 

14 

10 

71.4 

1888 

3 

1 

33.3 

1902  _, 

21 

15 

71.4 

1889 

3 

3 

100 

1903  -, 

14 

9 

64.2 

1890 

1 

1 

100 

1904  -, 

11 

9 

81.8 

1891 

6 

4 

-   66.6 

1905  — 

1892 

3 

1 

33.3 

1906  __ 

1893 

4 

2 

50 

1907  __ 

--- 

---- 

1894 

0 

0 

0 

1908  — 

5~" 

1895 

3 

3 

100 

1909  __ 

28 

13 

46.4 

1896 

6 

6 

100 

1910  — 

19 

14 

73.6 

1897 

6 

5 

83.3 

1911  _, 

16 

6 

37.5 

1898 

3 

3 

66.6 

(*) 

i 

2 

50 

•Year  not  definitely  known. 


It  might  be  well  to  point  out  at  this  time  the  necessity  for  the 
careful  collection  of  data  regarding  the  occurrence  of  cases  in  the 
various  infected  states.  Rocky  Mountain  spotted  fever  certainly 
should  be  put  on  the  list  of  reportable  diseases. 


SYMPTOMS    IN    MAN. 

Passing  now  to  the  consideration  of  the  clinical  aspects  of  the 
disease  in  man,  Maxey's  definition  of  the  disease  may  be  modified 
to  read.  Rocky  Mountain  spotted  fever  is  an  acute,  endemic, 
febrile  disease,  occurring  chiefly  during  the  summer  months, 
transmitted  by  the  bite  of  the  tick,  and  characterized  clinically 
by  a  continuous  moderately  high  fever,  severe  arthritic  and  mus- 
cular pains,  and  a  profuse  petechial  or  purpuric  eruption  in  the 
skin,  appearing  first  on  the  ankles,  wrists,  and  forehead,  but  rap- 
idly spreading  to  all  parts  of  the  body. 

After  an  incubation  period  varying  from  three  to  ten  days, 


ROCKY  MOUNTAIN  SPOTTED  FEVER.  7 

usually  seven,  during  which  the  patient  may  feel  indisposed  and 
complain  of  ill-defined  sensations  of  cold,  nausea  and  weariness, 
there  is  a  frank  chill.  If  seen  at  that  time,  the  patient  will  gen- 
erally complain  of  pain  and  soreness  in  the  muscles,  bones  and 
joints,  especially  in  the  lower  lumbar  region.  Severe  occipital 
headache  and  photophobia  are  frequent  symptoms  and  the  face 
may  appear  flushed  and  swollen.  Epistaxis  commonly  occurs  and 
constipation  is  the  rule.  The  severity  of  the  symptoms  varies  in 
individual  cases  and  is  less  severe  in  Idaho  than  in  Montana. 

Upon  examination  the  face  is  apt  to  be  flushed,  and  the  con- 
junctivae congested  and  yellowish.  The  tongue  is  covered  cen- 
trally with  a  heavy,  white  coat  while  its  tip  and  edges  are  bright 
red.  A  slight  bronchitis  may  exist  and  the  urine  is  scanty  and 
may  contain  small  amounts  of  albumin  and  a  few  casts.  Prior  co 
the  initial  chill  there  may  be  a  little  afternoon  fever,  but  with  the 
chill  there  is  an  abrupt  elevation  of  temperature  and  on  the  suc- 
cessive days  there  is  an  evening  rise  with  slight  morning  remis- 
sions. At  any  time  from  the  eighth  to  the  twelfth  day,  usually 
the  tenth,  the  fastigium  is  reached  when,  if  the  patient  is  to  re- 
cover, a  fall  by  lysis  takes  place,  the  curve  reaching  subnormal 
from  the  fourteenth  to  the  eighteenth  day  and  remaining  so  for 
three  or  four  days.  In  certain  of  those  cases  which  do  not  reco/er 
there  is  a  continuous  fever  of  105°  F.  or  higher.  In  other  cases 
there  is  a  sharp  drop  in  the  temperature  curve  followed  by  a  sud- 
den rise  just  before  death. 

The  pulse  is  very  rapid  and  apt  to  be  thready.  There  is  a  pro- 
gressive decrease  in  tlie  erythrocytes  and  haemaglobin.  A  leu- 
cocytosis  with  considerable  increase  in  the  large  mono-nuclears 
occurs. 

The  respiration  rate  is  increased  in  proportion  to  the  pulse.  An 
initial  bronchitis  is  not  uncommon  and  hypostatic  pneumonia 
sometimes  occurs. 

Usually  on  the  third  day  (sometimes  on  the  fourth)  the  erup- 
tion appears  on  the  wrists  and  ankles,  first  as  a  macular  roseola, 
which  as  it  spreads  to  the  arms,  legs,  forehead,  back,  chest  and 
abdomen,  in  the  order  named,  becomes  papular  and  may  terminate 
in  indefinate  blotches  or  petechiae  which  may  become  large 
ecchymotic  spots.  In  severe  cases  even  the  palms,  soles  and 
scalp  may  be  invaded.    From  twelve  to  forty-eight  hours  are  re- 


8  P.  A.  SURGEON  W.  C.  RUCKER. 

quired  for  the  rash  to  reach  the  maximum.  The  macules  vary 
in  size  from  a  pinpoint  to  a  split-pea  and  are  bright  red  except 
when  the  case  is  unusually  severe  when  they  are  dark  purple. 
Not  infrequently  they  assume  this  color  after  death.  It  was  this 
sign  which  caused  the  earlier  cases  to  be  called  "the  blue  disease" 
or  "black  measles."  The  macules  disappear  readily  on  pressure 
rapidly  to  return — the  papules  do  not  disappear  on  pressure  until 
the  patient  is  progressing  to  recovery.  With  the  fall  in  the  fever, 
the  eruption  begins  to  fade,  but  for  a  considerable  time  after  re- 
covery it  may  reappear  as  a  subcuticular  mottling  after  free 
perspiration  or  a  warm  bath.  Cases  have  been  reported  in  which 
there  was  no  exanthem.  Late  in  convalescence  there  is  a  gen- 
eralized desquamation.  Gangrene  of  the  ears,  fauces,  fingers  or 
toes,  scrotum,  penis,  or  entire  pudenda  may  occur  as  distressing 
sequelae.  Haematogenous  jaundice  usually  occurs  and  in  addi- 
tion the  face  may  have  a  bloated  appearance  erasing  the  lines  of 
expression  and  giving  it  a  stupid  look. 

The  teeth  are  covered  with  sordes  early  and  the  tongue  is 
coated  throughout  the  disease.  This  coating  is  at  first  white,  but 
later  it  becomes  light  yellow  and  finally  dirty  brown.  The 
mouth  is  dry  and  cracked.  Constipation,  sometimes  extreme,  ex- 
ists throughout  the  disease.  Initial  nausea  which  may  extend 
throughout  the  disease  is  not  uncommon.  There  is  splenic  and 
hepatic  enlargement. 

The  urine  is  high  colored,  acid  and  reduced  in  amount.  Albu- 
min and  granular,  hyaline  and  epithelial  casts  are  found  in  about 
fifty  per  cent  of  the  cases.    Haemaglobinuria  almost  never  occurs. 

The  mind  is  usually  clear  throughout  the  disease.  During  the 
period  of  invasion  there  may  be  restlessness  and  insomnia  owing 
to  the  attendant  pain  in  the  bones  and  muscles.  Later  this  is  ab- 
sent. Kernig's  sign  is  not  found.   Ocular  symptoms  are  very  rare. 

SYMPTOMS    IN    ANIMALS. 

The  reactions  which  occur  when  laboratory  animals  are  inocu- 
lated with  the  disease  are  fairly  constant.  Guinea  pigs  when 
given  0.5  cc  to  5.0  cc  of  defibrinated  infected  blood,  serum  or 
washed  corpuscles,  subcutaneously  or  intra-peritoneally  present  a 
rise  of  temperature  after  an  incubation  period  varying  from  two 
to  five  days.    From  the  fifth  to  the  seventh  day  the  temperature 


ROCKY  MOUNTAIN  SPOTTED  FEVER.  9 

may  reach  107.6°  F.  Coincident  with  the  fastigium,  the  scrotum 
and  testicles  become  swollen  and  oedematous  and  subsequently  the 
overlying  skin  of  the  pudenda  becomes  the  seat  of  hypodermic 
haemorrhages  of  varying  size  and  outline.  Vulvar  changes  occur 
in  female  guinea  pigs,  but  are  less  constant.  The  soles  of  the  fe^t 
and  the  ears  are  red  and  congested,  and  if  the  animal  be  depilated, 
reddish  macules  may  be  observed  on  the  dorsal  and  lateral  aspects 
of  the  body.  Emaciation  is  rapid,  and  death  usually  occurs  from 
the  seventh  to  the  eleventh  day.  Recovery,  when  it  takes  place,  is 
gradual  and  may  be  accompanied  with  scrotal  sloughing,  followed 
by  deforming  cicatrix  formation.  There  is  desquamation  of  the 
soles  of  the  feet  and  the  ears  become  dry  and  brittle,  subsequently 
dropping  off  leaving  a  short  thickened,  irregular  stump.  The 
animal  is  emaciated  and  may  not  regain  its  normal  weight  for 
several  weeks.  When  the  disease  is  transmitted  by  ticks  the  signs 
are  much  the  same,  except  that  there  may  be  areas  of  necrosis  and 
patchy  alopecia  at  the  points  where  the  ticks  attached. 

In  monkeys  {Macacus  rhesus),  the  disease  produces  cyanosis 
of  the  face  and  ears,  a  skin  eruption  varying  from  an  erythema  to 
a  macular  and  petechial  marking  distributed  over  the  external 
aspects  of  the  arms,  legs,  buttocks  and  back.    The  scrotum  a: 
penis  are  enlarged  and  haemorrhagic. 

The  rabbit  (Lepus  sp.)  is  mildly  susceptible  to  the  virus,  but  in 
far  less  severe  form  than  in  guinea  pigs  and  monkeys.  After  an 
incubation  period  varying  from  three  to  six  days,  the  temperature 
reaches  104°  F.  and  falls  by  lysis.  Aside  from  congestion  of  the 
scrotum  no  marked  anatomical  changes  have  been  recorded.  The 
susceptibility  of  the  various  domestic  animals  and  the  mammals 
of  the  infected  zone  will  be  discussed  elsewhere. 

PROGNOSIS. 

In  the  Idaho  cases,  the  prognosis  seems  to  be  very  favorable,  as 
a  rule  the  mortality  averaging  less  than  4%.  The  disease  is  far 
more  lethal  in  Montana  and  there  the  mortality  averages  close  to 
75%,  although  in  some  years  it  has  fallen  as  low  as  33.3%.  Death 
.  may  occur  as  early  as  the  third  or  as  late  as  the  eighteenth  day  of 
the  disease.  In  general,  if  the  patient  survive  the  tenth  day,  the 


10  p.  A.  SURGEON  W.  C.  RUCKER. 

prognosis  is  far  more  favorable.  Continuously  high  fever  or  a 
sudden  drop  in  temperature  are  grave  signs  as  is  also  delirium  or 
loss  of  consciousness. 

GROSS  PATHOLOGY. 

The  pathological  changes  are  not  extreme  but  they  are  fairly 
characteristic.  In  man,  rigor  mortis  usually  appears  early  and  is 
intense.  The  skin  changes  observed  at  necropsy  are  practically 
the  same  as  those  seen  ante-mortem  and  include  the  small  wounds 
the  result  of  tick  bites.  Icterus  is  constant  and  cutaneous 
haemorrhages  of  varying  sizes  and  shape  are  usually  seen.  In  the 
Idaho  cases,  gangrene  of  the  fauces,  tonsils,  and  palate,  and  of  the 
scrotum,  penis,  and  vulva  have  been  noted.  Aside  from  occa- 
sional hypostatic  congestion  and  a  rare  pneumonia,  the  respiratory 
apparatus  is  usually  normal.  Epicardial  haemorrhages  over  the 
ventricles  were  constantly  found  in  Anderson's  cases  (2).  The 
heart  muscle  is  flabby,  soft  and  pale.  The  right  heart  is  usually 
full  of  firmly  coagulated  blood  while  the  left  heart  is  contracted 
and  empty.  The  spleen  is  usually  enlarged  to  three  or  four  times 
its  normal  weight,  is  dark  purple,  soft  and  very  friable.  The  liver 
is  enlarged  and  shows  cloudy  swelling  and  fatty  degeneration. 
The  pancreas  is  about  twice  its  normal  weight.  The  intestines 
may  show  submucous  haemorrhages.  Le  Count  (28)  notes  the 
enlargement  of  the  superficial  and  visceral  lymph  glands.  The 
kidneys  are  usually  enlarged  and  present  subcapsular  and  pelvic 
haemorrhages.  The  other  abdominal  viscera  are  not  markedly 
affected.  The  changes  in  the  nervous  system  are  not  constant 
enough  to  be  of  value  in  the  post-mortem  diagnosis  of  the  disease. 

In  guinea  pigs,  the  pathological  changes  noted  include  coagula- 
tion necrosis  about  the  site  of  inoculation;  enlargement  of  the 
superficial  lymph  glands  with  central  haemorrhages  and  degenera- 
tion; splenic  and  hepatic  changes  similar  to  those  observed  in 
man;  enlargement  of  the  supra-renal  bodies;  localized  haemor- 
rhages with  necrosis  of  the  pudenda ;  and  gangrenous  changes  of 
the  ears.  The  lesions  in  monkeys  are  practically  identical  with 
those  observed  in  man. 

MICROSCOPIC  PATHOLOGY. 

The  microscopic  "changes  are  of  two  sorts,  those  connected 


ROCKY  MOUNTAIN  SPOTTED  FEVER.  11 

with  the  occlusions  of  vessels  and  the  more  diffuse  lesions  affect- 
ing entire  groups  of  organs.  The  diffuse  changes  are  hyperplasia 
of  lymphoid  tissues  and  cloudy  swelling  and  acute  fatty  changes  in 
organs  commonly  the  seat  of  such  lesions  in  acute  infectious 
diseases.  The  focal  lesions  are  more  varied  in  their  nature  since 
they  include  not  only  the  processes  leading  up  to  the  occlusion  of 
vessels,  but  the  results  of  such  obstructions,  necrosis  in  different 
degrees  and  the  haemorrhages  responsible  for  so  many  of  the 
clinical  and  gross  anatomic  features  of  the  disease  as  well  as  for 
the  name  'spotted  fever'  (28)."  The  minute  changes  have  been 
made  the  subject  of  a  careful  study  by  Le  Count  (28)  to  whose 
article  the  reader  is  referred. 

TREATMENT. 

Many  methods  of  treatment  have  been  advised  and  employed 
in  the  attempt  to  cure  this  disease.  They  run  the  gamut  of  the 
pharmacopoea  from  sage  tea  to  quinine  and  they  have  returned  to 
that  tacit  admission  of  ignorance  "good  nursing  and  symptomatic 
medication."  Ricketts  (52,  54),  has  produced  a  protecti\e  (and 
if  given  very  early,  and  in  large  doses,  curative)  serum  which 
Heinemann  and  Moore  (22)  have  attempted  to  concentrate.  The 
number  of  cases  in  which  it  has  been  used  is  too  small  to  judge 
of  its  efficacy.  Dr.  Karl  Kellogg  of  Stevensville,  Montana,  and 
Dr.  J.  Wilson  Reed  of  Victor,  Montana,  have  each  used  sodium 
caccodylate  with  apparent  success  in  a  single  case,  but  until  we  are 
better  informed  as  to  the  etiology  of  the  disease  all  attempts  at  its 
cure  must  be  empirical  and  groping. 

ETIOLOGY. 

When  we  attempt  the  consideration  of  the  etiology  of  this 
disease  we  are  in  a  certain  measure  entering  a  terra  incognita. 
As  noted  by  Maxey  (32),  in  his  original  paper,  spotted  fever  is  a 
"place"  disease,  being  definitely  limited  to  a  certain  locality,  for 
example,  to  a  single  side  of  a  valley.  It  is  also  rather  sharply 
limited  to  a  definite  season  of  the  year,  usually  to  the  months  of 
March,  April,  May,  June  and  July.  It  attacks  all  ages  and  both 
sexes,  although  the  greater  number  of  cases  have  occurred  in 
males  between  30  and  40  years  of  age.  Persons  whose  occupa- 
tions take  them  into  the  wooded  foothills  seem  more  liable  to  the 
disease,  therefore  the  bulk  of  the  cases  have  occurred  in  lumber- 


]2  7'.  A.  SURGEON  W.  C.  RUCKER, 

men,  miners,  prospectors,  ranchers,  and  sheepherders,  and  bridge 
builders,  carpenters,  civil  engineers  and  others  concerned  in  rail- 
road construction  work.  It  is  apparently  non-contagious,  more 
than  a  single  case  rarely  occurring  in  a  given  household  at  the 
same  time.  It  has  been  impossible  to  incriminate  water  or  food 
of  any  kind  as  the  vehicles  of  infection,  although  when  Maxey 
presented  his  first  paper  he  suggested  that  the  drinking  of  snow 
water  might  be  the  means  of  receiving  the  disease. 

THE  TICK  HOST. 

Wilson  and  Chowning  in  their  original  report  (72)  suggested 
the  hypothesis  that  the  wood-tick  {Dermacentor  andersoni)  acted 
as  the  transmitting  agent  and  offered  in  support  of  this  theory 
several  facts  which  may  be  thus  summarized : 

1.  The  appearance  of  the  disease  is  coincident  with  the  period  of  ac- 
tivity of  the  wood-tick. 

2.  The  disappearance  of  the  disease  is  coincident  with  the  disappear- 
ance of  the  wood-tick. 

3.  The  limitation  of  the  disease  in  a  certain  locality  suggests  the  con- 
veyance of  the  germ  to  man  by  a  temporary  parasite  "traveling  slowly  and 
not  widely  and  which  is  not  carried  far  by  the  wind.  The  tick  answers  this 
description." 

4.  The  great  bulk  of  patien-ts  give  a  history  of  having  been  bitten  by 
ticks  prior  to  their  illness. 

5.  Mosquitoes  may  be  eliminated  from  the  problem  because  their  ap- 
pearance and  disappearance  does  not  coincide  with  that  of  spotted 
fever;  because  of  their  lack  of  geographic  limitation;  and  because  they 
would  be  more  apt  to  bite  and  thus  infect  a  greater  number  in  a  given 
family.  Bedbugs  and  fleas  are  omnipresent  and  perenial — spotted  fever 
is  not. 

Cobb  (13),  Anderson  (i,  2),  Westbrook  (56),  and  R.  W. 
Smith  (56),  coincided  in  this  view,  but  Stiles  (64),  was  "unable 
to  confirm  this  hypothesis."  Ashburn  (5)  reached  the  same  con- 
clusions as  Stiles.  In  1906,  King  (27)  succeeded  in  transmitting 
the  disease  from  one  guinea  pig  to  another  guinea  pig  by  an  adult 
male  tick  and  Ricketts  (41-46)  was  able  to  similarly  transfer  the 
infection  by  an  adult  female  tick.  The  following  year,  1907,  Rick- 
etts (45)  demonstrated  that  infected  ticks  exist  in  nature  on  the 
west  side  of  the  Bitter  Root  Valley  of  Montana  and  by  their  bites 
he  reproduced  the  disease  in  guinea  pigs.  He  further  showed  that 
the  larvae  and  the  nymphs,  and  both  adult  male  and  female  ticks 


ROCKY  MOUNTAIN  SPOTTED  PEVER.  13 

infected  by  feeding  on  an  infected  animal  may  transmit  the 
disease  to  normal  susceptible  animals :  that  larvae  and  nymphs 
may  acquire  the  disease  in  a  similar  manner  and  that  they  are 
capable  of  transmitting  it  in  their  subsequent  stages  of  develop- 
ment: that  infected  females  may  transmit  the  disease  to  their 
young  through  their  eggs :  that  the  infection  is  generalized  in  the 
body  of  infected  ticks :  that  the  virus  remains  active  in  the  body 
of  the  nymphal  tick :  that  infected  ticks  are  infective  as  long  as 
they  live  and  will  bite.  From  the  foregoing,  it  may  be  deduced 
that  the  tick  is  the  disseminator  of  the  causal  agent  of  the  disease 
in  nature.  As  a  final  and  clinching  proof,  McCalla  (34)  re- 
moved a  tick  from  a  man  suffering  with  the  disease,  and  with 
their  consent,  infected  a  man  and  a  woman  by  its  bite. 

Since  it  has  been  proven  that  the  disease  exists  in  ticks  in  na- 
ture, it  is  to  be  expected  that  the  distribution  of  the  disease  is  the 
same  as  the  distribution  of  the  dermacentor.  This  has  been  made 
the  subject  of  a  study  by  Bishop  (9)  and  while  Rocky  Mountain 
spotted  fever  has  not  been  reported  from  the  entire  life  zone  of 
this  tick,  with  the  exception  of  the  cases  which  occurred  in  the 
Klondike,  the  disease  has  not  been  found  outside  the  area  which 
the  tick  infests.  This  includes  the  northern  part  of  the  Rocky 
Mountain  region  in  the  United  States,  and  the  river  valleys  and 
sagebrush  plains  to  the  west,  the  western  corner  of  South  Dakota, 
almost  the  entire  states  of  Montana,  Wyoming  and  Colorado,  the 
northern  portion  of  New  Mexico,  Utah  and  Nevada,  all  of  the 
state  of  Idaho,  the  eastern  half  of  Washington  and  Oregon,  and 
the  northeastern  corner  of  California.  It  also  occurs  in  southern 
British  Columbia,  and  eastern  Alberta. 

There  has  been  more  or  less  discussion  regarding  the  taxonomy 
of  this  species,  but  that  is  a  question  for  zoological  nomenclatur- 
ists  which  need  not  be  considered  here,  and  it  should  be  borne  in 
mind  that  Maver  (31)  has  transmitted  the  disease  by  three  other 
species,  Dermacentor  marginatus  (Utah),  Amhlyomma  Ameri- 
canum,  Linnaeus,  (Missouri)  and  Dermacentor  variabilis, 
(Mass.).  It  may  be  of  profit,  however,  to  describe  briefly  the  com- 
monest form  {D.  andersoni)  and  to  outline  its  life  history,* 


♦The  writing's  of  Stiles  (68,  69)  and  Ricketts  have  been  freely  drawn 
upon  in  the  preparation  of  this  description.  For  a  more  technical  con- 
sideration of  the  subject  the  reader  should  consult  Bull.  62.  U.  S.  Pul). 
Health  and  Mar.  Hos.  Serv.,  Hyg.  Lab.,  1910. 


14  P.  A.  SURGEON  IV.  C.  RUCKER. 

THE  ANATOMY   Ol-"   TICKS. 

Ticks,  superfamily  Ixodoidea,  order  Acarina,  class  Arachnida, 
represent  the  giant  mites.  Anatomically  a  tick  may  be  divided 
into  a  head,  rostrum,  or  capitulum,  and  a  body.  The  capitulum 
consists  of  a  neck  which  connects  it  with  the  body ;  a  hard,  usually 
quadrangular  portion  called  the  base,  which  presents  two  porose 
areas  and  supports  the  palpi,  which  are  composed  of  four  seg- 
ments, the  hypostome,  and  elongated  structure  in  symmetrical 
halves,  which  are  covered  with  minute  recurving  teeth,  and  the 
mandibles  or  biting  apparatus.  The  body  is  more  or  less  ovoid  in 
shape  and  varies  greatly  in  form,  color,  outline  and  structure  in 
the  different  species  and  at  different  periods  of  development. 
The  body  is  divided  for  purposes  of  description  into  a  dorsal  sur- 
face, a  ventral  surface,  and  anterior,  posterior,  and  lateral  mar- 
gins. The  dorsal  surface  presents  a  hard,  chitinous  plate,  marked 
by  two  longitudinal  grooves.  This  is  called  the  scutum  and  is 
smaller  in  the  female  than  in  the  male.  The  eyes  are  seen  at  each 
lateral  margin  of  the  scutum  and  on  each  side  of  the  median  line, 
near  the  third  and  fourth  legs,  are  small,  oval,  chitinous  structures 
called  the  dorso-submedian  porose  plates.  Along  the  posterior 
margin  of  the  body  are  the  postero-marginal  festoons,  eleven  in 
number.  The  ventral  surface  presents  for  examination  the  genital 
pore,  situated  between  the  coxae  of  the  first  three  pairs  of  legi-; 
the  anus,  similarly  situated  in  the  median  line  but  behind  the  pot;- 
terior  pair  of  legs;  and  the  stigmal  plates  placed  laterally  just  be- 
liina  tiie  tourtli  pair  of  legs.  The  anterior,  posterior,  and  lateral 
margins  vary  in  the  different  species.  The  legs  are  four  in  number 
on  each  side  and  each  is  seg.nented  into  a  cova,  trochanter, 
femur,  patella,  tibia,  and  tarsus.  Both  the  dorsal  and  the  ventral 
surfaces  present  grooves,  pits,  hairs  and  spines  which  are  of  value 
in  distinguishing  the  various  species.* 

THE  DERMACENTOR  ANDERSONI. 

The  Dermacentor  andersoni  Stiles  (1905),  male  is  oval,  narrov/ 


•For    a    description    of    tlie    internal    anatomy    see    CHRISTOPHERS, 
(S.  R.)     The  anatomy  and  histology  of  ticks.     Calcutta,  1906, 


.       ROCKY  MOUNTAIN  SPOTTED  VEVHR.  15 

in  front,  broad  behind,  with  scutum  variegated  brown  and 
white.  Anteriorly  there  is  an  elliptical  area,  called  the  pseudo- 
scutum,  limited  by  a  white  border  and  possessing  two  lateral 
brown  stripes,  with  a  median  brown  stripe  or  spots  between  them. 
Behind  this  there  are  four  brown  stripes  arranged  in  a  curve,  open 
anteriorly.  Posterior  to  these  there  are  usually  five  brown  stripes, 
one  central  and  two  on  each  side.  Elsewhere  the  whole  dorsum  is 
speckled  with  small  brown  dots.  The  eleven  festoons  of  the  pos- 
terior border  are  roughly  quadrangular  in  outline  and  consist  of 
a  white  area  with  one  brown  spot  and  small  brown  specks.  On 
the  ventral  surface,  it  is  noted  that  the  first  coxae  arise  by  two 
roots,  bidentate,  while  the  others  arise  by  a  single  spine.  The 
fourth  coxa  is  very  large,  being  two  or  three  times  the  size  of  the 
third.  Opposite  the  second  pair  of  legs  is  the  genital  aperature. 
The  stigmal  plates  are  somewhat  comma  shaped.* 

The  non-engorged  female  is  about  the  same  size  as  the  male,  5 
by  2.5  millimetres.  The  body  is  oval  and  broader  posteriorly  than 
anteriorly.  The  scutum  extends  as  far  back  as  the  third  pair  of 
legs  and  is  marked  like  the  corresponding  portion  of  the  scutum 
of  the  male.  There  is  a  dorsal  marginal  groove  and  three  longi- 
tudinal grooves.  Eleven  festoons  on  the  posterior  margin.  The 
genital  aperature  on  the  ventral  surface  is  opposite  the  second 
coxa  and  from  it  the  genital  grooves  run  backward  diverging  lat- 
erally behind  the  fourth  coxa  and  ending  between  the  second  and 
third  external  festoons.  There  is  a  short  anomarginal  groove. 
The  replete  female  is  about  16  by  10  millimetres  and  deep  brown 
or  slate  color. 

LIFE  HISTORY  D.  ANDERSONI. 

The  adult  male  and  female  feed  in  common  on  various  mam- 
mals and  it  is  during  this  time  that  copulation  and  fertilization 
takes  place.  The  female  continues  to  feed  for  several  days  after 
fertilization  until  she  has  become  a  slate  colored,  swollen  ovoid 


•See  Stiles'  "The  taxonomic  value  of  the  microscopic  structure  of  the 
stigmal  plates  in  the  tick  genus  Dermacentor."  Bull.  62.,  U.  S.  Pub. 
Health  and  Mar.  Hos.  Serv.,  Hyg.  Lab.,   1906. 


16  P.  A.  SURGEON  IV.  C.  RUCKBR. 

body.  This  increase  in  size  is  due  to  the  ingestion  of  blood  from 
the  host  and  the  enlargement  of  the  ovaries  and  beginning  forma- 
tion of  hundreds  or  even  thousands  of  minute  eggs.  After  com- 
plete engorgement,  the  female  drops  from  the  host  and  after  a 
resting  period  of  about  two  weeks  begins  oviposition.  To  accom- 
plish this  the  head  is  bent  ventrally  until  the  capitulum  rests  on  the 
edge  of  the  genital  opening.  At  the  same  time  there  is  protruded 
from  beneath  the  scutum  a  delicate  white  gelatinous  membrane 
which  terminates  in  two  delicate  cones  covered  with  an  adhesive 
secretion.  The  extrusion  of  this  membrane  covers  the  head  and 
as  the  two  small  sticky  cones  reach  the  genital  orifice  the  egg  is 
expelled  on  to  them.  The  membrane  is  then  withdrawn  and  the 
head  extended,  the  egg  resting  on  the  front  of  the  scutum.  In 
this  way  an  adherent  mass  of  eggs  gradually  forms  in  front  of 
the  tick.*  Unless  observed  closely  it  appears  as  though  the  eggs 
were  being  extruded  from  beneath  the  scutum.  As  this  process 
continues  the  tick  begins  to  shrivel  and  at  the  end  of  oviposition 
it  dies.  The  number  of  eggs  deposited  varies  from  several  hun- 
dred to  three  thousand. 

The  length  of  time  before  the  eggs  begin  to  hatch  depends  on 
the  surrounding  temperature.  In  the  summer  months,  it  is  from 
thirty  to  fifty  days,  but  in  the  cold  season  it  may  be  delayed  for 
several  months.  From  the  egg  appears  the  larval  form  of  "seed- 
tick"  stage.  These  are  minute  specks  which  are  first  pale  and 
soft,  and  later  become  covered  with  a  hard  brown  coating.  They 
have  six  legs  and  are  without  genital  and  spiracular  orifices.  They 
are  seen  in  nature  in  clumps  on  blades  of  grass  or  twigs  where 
they  wait  with  outstretched  legs  for  passing  mammals.  Having 
attached  themselves  to  a  warm-blooded  host  they  feed  to  engorge- 
ment in  about  six  days.  During  this  time  the  original  bulk  is  in- 
creased many  fold,  reaching  about  the  size  of  a  head  of  a  pin.  The 
color,  which  depends  on  the  character  of  the  food  taken,  blood  or 
serum,  varies  from  light  pink  to  dark  brown.  Having  fed  to  sur- 
feitment,  the  tick  drops  off  and  lies  dormant  for  about  four  weeks 


•See  BRAUN,  (M.),  "The  animal  parasites  of  man."    "Wm.  Wood  &  Co., 
N.  Y.,  361. 


ROCKY  MOUNTAIN  SPOTTED  FEVER.  17 

prior  to  moulting.  Here  again  the  time  varies,  being  as  short  as 
two  weeks  and  as  long  as  two  months.  Unless  the  larvae  se- 
<l$ure  food  within  two  or  three  weeks  after  hatching  they  die. 
Aftgr  the  larval  skin  is  cast,  the  nymph  having  four  pairs  of 
legs  and  spiracular  orifices  but  no  genital  aperature,  emerges.  It 
is  about  1.5  millimetres  in  length  and  is  at  first  slightly  yellow  in 
color  but  after  feeding  becomes  brownish  black.  Again  it  awaits 
a  host  and  having  secured  one  feeds  from  four  to  eight  days,  be- 
coming greatly  enlarged,  4  by  2  millimetres,  and  eventually  drop- 
ping off  as  in  the  previous  stage  of  its  development.  It  does  not 
immediately  re-enter  the  dormant  state  but  may  be  active  for  a 
period  varying  from  two  to  four  weeks.  This  is  apparently  in- 
fluenced by  the  atmospheric  temperature.  Eventually,  however, 
it  becomes  quiescent  and  lies  dormant  for  about  a  month  while 
the  metamorphosis  into  the  adult  is  being  completed.  When  this 
is  completed  a  second  moult  takes  place  and  it  emerges  from  the 
snowy  white  shell,  a  mature  tick  with  genital  orifices  and  the  sec- 
ondary sexual  characteristics  typical  of  the  male  or  female.  The 
adults  now  attach  themselves  to  a  warm-blooded  host  and  after 
a  time  copulation,  fertilization  and  oviposition  take  place  and  the 
cycle  is  recommenced.  It  is  believed  that  the  tick  produces  but 
one  brood  a  year.  It  may  be  noted  also  that  Cooley  (15)  quotes 
W.  V.  King  of  the  Montana  Agricultural  College  as  suggesting 
the  hypothesis  that  the  life  cycle  of  this  tick  {D.  andersoni)  is 
two  years.  Additional  experimental  evidence  seems  needful  to 
prove  this. 

MAJHMALIAN   HOSTS  OF  THE)  D.  ANDERSONI. 

It  is,  of  course,  important  that  we  know  what  animals  act  as  the 
hosts  for  these  ticks.  This  has  not  only  a  direct  bearing  on  tick 
control  but  it  may  also  lead  us  to  the  discovery  of  the  animal 
which  acts  as  the  intermediary  host  for  the  virus,  provided,  of 
course,  that  such  is  necessary  for  the  perpetuation  of  the  disease. 
Data  has  therefore  been  collected  bearing  on  this  important  aspect 
of  the  question. 


18 


P.  A.  SURGEON  W.  C.  RUCKER. 


Animals  on  Which  the  D.  Andersoni  has  been  Found,  Their  Susceptibil- 
ity to  Rocky  Mountain  Spotted  Fever,  and  the  Stage  of  Development 
of  the  Tick. 


Animal. 


Mule  deer  (Odocoileus  hemionus)  . . 

Elk   (Cervus  canadensis) 

Mountain  goat  (Oreamnos  mon- 
tanus)     • . . . 

Mountain  sheep  (Ovis  canadensis) . . 

Pine  squirrel  (Sciurus  hudsonicus 
richardsoni)    

Yellow  bellied  chipmunk  {Eutamias 
luteiventris)    

White  bellied  chipmunk  {Eutamias 
quadrivittatus  umbrinus) 

Columbian  ground  squirrel  (Citellus 
columhianus)     

Side  striped  ground  or  rock  squir- 
rel {Callospermophilus  lateralis 
cinerascens) 

Woodchuck  {Marmota  flaviventris) . 

White-footed  mouse  (Peromyscus 
maniculatus  artemisioe) 

Wood  rat  (Neotoma  cinerea) 

Meadow  mouse  (Microtus  modes- 
fus)   

Porcupine  (Erethison  epixanthum).. 

Rock  cony  or  rabbit  (Ochotona 
princeps) 

Snowshoe  rabbit   (Lepus  bairdi) 

Cottontail  rabbit  {Sylvilagus  nut- 
tali)    

Coyote    ( Canis  testes) 

Badger   ( Taxidea  taxus) 

Weazel  {Putorius  arizonensis) . . 

Black  bear   (Ursus  americanus) 

Marten   (Mustela  c.  origenes)  . . 

Dog  {Canis  familiaris) 

Cow  {Bos  taiirus) 

Horse   {Equus  caballus) 

Sheep    ( Ovis   aries) 

Swine   {Sus  scrofa) 


Suscep- 
tible. 

Adult. 

Nymph. 

V 

+ 

+ 

s» 

+ 

9 

+ 

+ 

V 

+ 

? 

+ 

+ 

+ 

+ 

+ 

+ 

+ 

+ 

+ 

-|- 

+ 

-|- 

0 

+ 

+ 

4- 

0 

+ 

•? 

+ 

V 

-r 

+ 

? 

+ 

+ 

+ 

+ 

0 

+ 

0 

+ 

+ 

+ 

V 

+ 

y 

— 

y 

-- 

6 

+ 

+ 

+ 

0 

+ 

0 

rf 

Lar- 
vae. 


+ 
+ 

+ 


+ 
+ 


+ 


In  studying  this  aspect  of  the  question,  Ricketts  endeavored  to 
determine  the  following  points  with  regard  to  the  ground  squirrel, 
the  ground  hog,  the  rock  squirrel,  the  chipmunks,  and  the  moun- 
tain or  wood  rat: 


I.  Is  the  animal  susceptible  to  the  disease  by  inoculation? 


ROCKY  MOUNTAIN  SPOTTED  FEVER. 


19 


2.  Is  the  animal  susceptible  to  the  disease  through  tick  bites? 

3.  Can  the  "tick  cycle"  be  completed  on  the  animal?     (i.  e.  receive 
the  disease  through  ticks  and  subsequently  infect  another  tick.) 

4.  Has  the  animal  the  disease  in  nature? 

The  results  of  his  experiments  may  thus  be  tabulated : 
Susceptibility  to  Rocky  Mountain  Spotted  Fever. 


Species. 


Inocula- 
tion. 


By 

bites. 


Tick 
cycle. 


Ground  squirrel 
Ground  hog. . . . 
Rock  squirrel.. 
Chipmunks  . . . . 
Mountain  rat  . . 


+ 

+ 
+ 
+ 
+ 


+ 

+ 
+ 
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MAJMMAI^IAN  HOSTS  FOR  THE  DISEASE. 

The  question  of  the  occurrence  of  the  disease  among  mammals 
in  nature  has  not  yet  been  solved,  although  considerable  work  has 
been  and  is  being  done  upon  it.  It  is  an  enormous  problem  and  in- 
volves the  examination  of  great  numbers  of  live  wild  animals,  the 
determination  of  their  immunity  to  spotted  fever  and  the  inocula- 
tion of  their  blood  into  laboratory  animals  to  find  out  if  they  (the 
wild  animals)  have  the  disease  in  acute  form.  These  points  must 
be  settled  if  we  would  discover  the  animal  which  perpetuates  the 
disease. 

THE  VIRUS. 

With  regard  to  the  virus  itself,  even  less  is  known.  Wilson  and 
Chowning  (72)  described  certain  ovoid  intra-corpuscular  bodies 
in  both  fresh  and  stained  blood  taken  from  persons  suffering  with 
spotted  fever.  Anderson  (i,  2,  3),  agreed  with  them  that  this 
organism,  which  they  named  "piroplasma  hominis,"  was  "very 
probably  the  cause  of  spotted  (tick)  fever."  Ashburn  (5)  and 
Stiles  (64-66)  failed  to  confirm  this  view  and  the  latter  stated 
that  "indications  are  not  lacking  that  at  least  some  of  the  stages 
of  the  supposed  piroplasma  hominis  consist  in  reality  of  vacuoles, 
blood  platelets,  blood  dust,  artifacts  and  tertian  malaria  para- 
sites."   Maxey,  Simon  and  Cole  found  no  piroplasms  in  the  blood 


20  P.  A.  SURGEON  IV.  C.  RUCKBR. 

of  cases  in  Idaho  and  neither  Ricketts  nor  Kieffer  secured  evidence 
which  convinced  them  of  the  existence  of  the  parasite  of  Wilson 
and  Chowning.  Francis  was  unable  to  find  the  organisms  and 
Craig  expressed  the  belief  that  the  supposed  piroplasms  were 
merely  degenerated  erythrocytes. 

Ricketts  (53)  described  a  pleomorphic  bacterium  which  he  be- 
lieved might  bear  a  causal  relation  to  the  disease.  The  form 
which  he  most  commonly  found  was  that  of  "two  somewhat 
lanceolate  chromatim-staining  bodies,  separated  by  a  small  amount 
of  eosin-staining  substance."  These  bodies  were  found  in  the 
blood  of  men,  animals  and  ticks  infected  with  the  disease,  and 
seemed  to  stain  best  with  Giemsa's  stain.  The  eggs  of  infected 
ticks  from  both  Montana  and  Idaho  were  found  to  contain  large 
numbers  of  minute  bi-polar-staining  bacilli,  apparently  in  various 
developmental  stages.  These  organisms  are  found  in  large  num- 
bers in  the  salivary  glands,  alimentary  sac  and  ovaries  of  infected 
females,  but  they  have  not  been  found  in  the  viscera  of  non-in- 
fected male  and  female  ticks.  This  bacillus  has  not  been  grown 
on  artificial  media.  Ricketts  suggested  for  it  the  name  "the 
bacillus  of  Rocky  Mountain  spotted  fever."  He  found  that  it 
does  not  agglutinate  with  low  dilutions  of  immune  human  serum 
but  agglutinates  distinctly  in  dilutions  of  i  to  10,  i  to  20,  and  i  to 
40.  It  does  not  agglutinate  with  the  higher  dilutions.  Normal 
human  serum,  on  the  contrary,  caused  clumping  in  a  dilution  of  i 
to  I,  a  very  slight  agglutination  in  i  to  10,  and  none  at  all  in  the 
higher  dilutions.  In  immune  guinea  pig  serum  complete  agglu- 
tination was  present  in  dilutions  up  to  i  to  160.  Normal  guinea 
pig  serum  produced  practically  no  agglutination  at  all.  Until  fur- 
ther proof  is  brought  forward  the  causal  role  of  Ricketts'  bacillus 
must  be  considered  as  unproven,  although  there  are  many  facts 
which  strongly  suggest  it  as  the  infecting  agent. 

Whatever  may  be  the  cause  of  Rocky  Mountain  spotted  fever, 
however,  several  facts  regarding  it  have  been  clearly  established. 
It  is  non-filtrable :  its  infectiousness  is  largely  destroyed  by  grind- 
ing it  in  a  ball  mill.  At  50°  C.  the  infectiousness  of  the  virus  is 
destroyed  in  25  or  30  minutes.  Infected  blood  kept  in  the  ice 
compartment  of  a  refrigerator  loses  its  infectiousness  after  15  or 
16  days.  The  pathogenicity  of  the  virus  is  lost  between  24  and  48 
hours  after  complete  dessication.    It  may  be  kept  alive  by  passage 


ROCKY  MOUNTAIN  SPOTTED  FEVER.  21 

through  guinea  pigs,  monkeys,  rabbits  and  ground  squirrels 
{Citelius  colmnhianus).  The  virus  is  present  in  the  body  fluids 
generally.    It  produces  a  rather  high  degree  of  immunity. 

Whether  the  organism  of  Rocky  Mountain  spotted  fever  be  a 
protozoon  or  a  bacterium  the  fact  that  it  is  transmitted  to  man  by 
the  bite  of  the  tick  suggests  the  necessity  of  some  host  mammal 
for  the  perpetuation  of  the  disease.  It  is  true  that  in  malaria,  the 
protozoon  disease  type,  the  hemameba  has  but  two  life  cycles,  but 
it  is  apparent  that  the  opportunities  for  biting  man  which  the 
short-seasoned  tick  possesses  are  infinitely  less  than  those  of  the 
anopheles.  Neither  is  the  disease  analagous  in  its  etiology  to  yellow 
fever  nor  to  the  tick  fever  of  Africa,  because  both  the  Stegomyia 
calopiis  and  the  Ornithodorus  moubata  are  essentially  domestic 
in  their  habits,  whereas  the  Dcrmacentor  andersoni  comes  in  con- 
tact with  man  only  accidentally.  Also  the  feeding  habits  of  this 
species  would  preclude  man  from  being  anything  but  an  acci- 
dental host.  Hereditary  transmission  to  the  eggs  of  infected  fe- 
males explains  how  the  disease  may  be  kept  alive  from  one  spring 
to  the  next  but  would  not  account  for  the  perpetuation  of  the 
disease  since  not  more  than  50%  of  the  females  transmit  the 
disease  to  their  young.  At  this  ratio,  when  it  is  considered  that 
on  account  of  the  many  accidents  of  nature,  only  a  small  percent- 
age reach  maturity  and  only  a  small  number  of  these  become  fer- 
tilized, it  would  be  a  matter  of  a  short  time  only  until  the  disease 
became  extinct  from  natural  causes. 

The  domestic  and  wild  animals  remain  to  be  considered  as  pos- 
sible hosts.  This  has  already  been  discussed  in  this  article  (pages 
645-647)  with  regard  to  the  wild  animals  and  among  them  the 
search  has  been  narrowed  down  to  a  few  small  mammals.  Among 
the  domestic  animals,  the  horse  has  a  relative  resistance  to  the 
disease,  while  the  ox,  sheep  and  the  fowl  have  a  demonstrated  re- 
sistance. Cats  and  dogs  may  possibly  play  a  part  in  keeping  the 
virus  alive,  but  it  is  extremely  improbable.  The  larger  wild  mam- 
mals such  as  deer,  elk,  bear,  etc.,  wander  over  wide  stretches,  cer- 
tainly into  districts  where  spotted  fever  does  not  prevail  and  are 
never  in  continuous  close  proximity  to  human  dwellings.  For  the 
present  they  may  be  eliminated  from  the  problem.  The  white- 
footed  mouse,  meadow  mouse,  coyotte  and  badger  are  apparently 
not  susceptible  to  the  disease  by  inoculation  and  since  r-'jbits  are 


22  P.  A.  SURGEON  IV.  C.  RUCKBR. 

infected  with  some  difficulty,  the  rock  cony,  snowshoe  rabbit,  and 
cottQn-tail  rabbit  may  be  dropped  from  consideration.  Of  the 
animals  which  remain,  the  ground  squirrel,  the  ground  hog,  the 
rock  squirrel,  the  chipmunk,  the  mountain  rat,  and  the  weazel 
seem  to  be  the  most  important.  On  account  of  the  prevalence  of 
the  ground  squirrel  (C.  columbianus)  in  the  infected  zone  this 
species  has  been  regarded  with  the  greatest  suspicion  although  it 
is  not  impossible  that  several  other  species  may  also  act  as  hosts 
for  the  virus.  The  small  mammals  mentioned  certainly  enter  the 
problem  as  sources  of  food  supply  for  the  tick. 

PROPHYLACTIC  AND  ERADICATIVE;  MEASURES. 

We  are  dealing  then  with  a  disease  whose  cause  and  interme- 
diary host  are  unknown,  but  whose  disseminating  agent  we  know 
and  can  attack.  For  the  present  the  tick  must  be  the  focal  point 
of  all  prophylactic  and  eradicative  measures.  Inasmuch  as  do- 
mestic stock  furnish  a  convenient  supply  of  food  for  the  tick 
during  its  various  developmental  stages,  and  that  the  female  tick 
is  fertilized  during  feeding,  the  killing  of  ticks  on  cattle,  horses 
and  sheep  is  of  great  importance.  This  is  accomplished  by  dip- 
ping the  tick  infested  animal  in  crude  oil  or  some  of  the  well 
recognized  arachnicides,  such  as  cresylic  acid,  the  arsenic  salts  or 
extract  of  tobacco.  This  should  be  done  at  frequent  intervals 
from  March  1st  to  July  15th  and  should  include  all  the  animals  in 
the  infected  zone.  If  for  any  reason  it  is  not  desired  to  dip  any 
particular  animal  the  ticks  may  be  picked  off  every  four  or  five 
days  and  destroyed. 

The  clearing  and  burning  of  land  is  a  useful  measure.  This 
kills  the  tick  directly  and  on  account  of  the  exposure  to  the  bright 
sunlight  prevents  the  hatching  of  the  eggs.  The  feeding  of  cattle 
in  tick-free  lots,  if  done  universally,  would  prevent  any  increase 
in  the  number  of  ticks.  The  alternation  of  pasture  has  been 
found  of  service  in  combatting  Texas  tick  fever  and  might  be  of 
use  in  the  eradication  of  Rocky  Mountain  tick  fever. 

The  slaughter  of  the  small  mammalian  hosts  has  long  been  con- 
sidered a  logical  measure.  This  applies  particularly  to  the  ground 
squirrels,  which  are  not  only  a  perineal  source  of  food  and  habita- 
tion for  the  larval  and  nymphal  ticks,  but  which  may  possiWy 
prove  to  be  the  intermediary  host  for  the  virus.    The  methods  to 


ROCKY  MOUNTAIN  SPOTTED  FEVER.  23 

be  used  in  the  destruction  of  these  pests  were  fully  described  in  a 
paper  presented  to  the  Association  at  the  1910  Annual  Meeting/" 
Personal  prophylaxis  is,  of  course,  very  important  and  includes 
the  wearing  of  tick-proof  clothing  by  all  persons  entering  the  in- 
fected zone  during  the  season  of  tick  prevalence  and  the  careful 
daily  search  of  the  body  for  ticks  which  may  have  attached  them- 
selves and  have  escaped  notice.  Ticks  should  be  removed  as  soon 
as  discovered.  In  doing  this  the  tick  should  be  given  a  gentle  pull 
lest  the  head  be  torn  off  and  left  in  the  skin  to  make  a  very  annoy- 
ing infection  nidus.  Another  way  to  remove  the  tick  is  to  grease 
it.  This  closes  its  respiratory  spiracles  and  causes  it  to  loosen  its 
hold  and  drop  off.  When  attached  very  firmly  and  for  some  time 
they  may  be  pried  off  by  a  needle  thrust  into  the  skin  immediately 
beneath  the  tick's  head.  After  the  removal  of  the  tick  the  wou.id 
should  be  cauterized  with  a  toothpick  dipped  in  95%  carbolic  acid. 
If  there  is  any  suspicion  that  the  tick  was  received  in  the  zone  of 
infection  the  bitten  person  should  be  given  a  protective  dose  of 
Ricketts'  serum. 

BIBLIOGRAPHY. 

Anderson,  (J.  F.) 

1.  Spotted  fever  {tick  fever)  of  the  Rocky  Mountains,  a  new  disease. 

Am.  Med.,  Phila.,  VI,  506-508. 

2.  Spotted  fever  {tick  fever)  of  the  Rocky  Mountains,  a  new  disease. 

Bull.     No.  14.  U.  S.  Pub.  Health  and  Mar-Hosp.  Serv.,  Hyg.  Lab., 
1903,  Govt.  Print.  Office.  " 
Anderson,  (J  F.)  and  Goldberger,  (J.) 

3.  On  the  relation  of  Rocky  Mountain  spotted  fever  to  the  typhus  fever 

of  Mexico.  Pub.  Health  Rep.,  U.  S.  Pub.  Health  and  Mar.-Hosp. 
Serv.,  Wash.,  1909,  XXIV,  1861. 
Anderson,  (R.) 

4.  Historical,  laboratory  and  clinical  observations  in  so-called  "Rocky 

Mountain  spotted  fever."  Utah  M.  J.  (Denver  Med.  Times),  1908-9, 
XXVII,  516-522. 

ASHBURN,  (P,    M.) 

5.  Piroplasma  Hominis  {?)-spotted  fever  in  Montana.     Lancet-Clinic, 

Cincin.,  1905,  n.  s.  LIV,  494-505- 

6.  A  suggestion  as  to  the  treatment  of  spotted  fever  of  Montana.    Lan- 

cet-Clinic, Cincin.,  1905,  n.  s.  LIV,  579-584. 


•Rucker,  (W.  C.) 

Enzootic   plague   in    the  United   States.     The   Mil.    Surg.,    Wash.    1911, 
XXVIII,  1-16. 


24  P.  A.  SURGEON  IV.  C.  RUCKBR. 

AsHBURN,  (P.  M.)  and  Craig,  (C.  F.) 

7.  A  comparative  study  of  Tsutsumushi  disease  and  spotted  fever  oj 

Montana..  Philip.  J.  Sc,  1908,  III,  1-14.    Also  Bos.  Med.  &  Surg.  J., 
1908,  CLVIII,  749-761. 
Banks,  (N.) 

8.  The  scientific  name  of  the  spotted-fever  tick.    J.  Am.  Med.  Ass.,  Chi- 

cago, 19 10,  LV,  1574-1575- 

BiRDSEYE,  (C.) 

See  Henshaw,  (H.  W.) 
BiSHOPp,  (F.  C.) 

9.  The  distribution  of  the  Rocky  Mountain  spotted  fever  tick.     U.  S. 

Dept.  Agric,  Bur.  of  Entomology,  Circ.  No.  136,  Wash.  Govt.  Print. 
Office,  191 1. 
See  also  Hunter,  (W.  D.) 
Castellani,  (A.)  and  Chalmers,  (A.  J.) 

10.  Spotted  fever  of  the  Rocky  Mountains.    Manual  of  Trop.  Med.,  Wm. 

Wood  &  Co.,  N.  Y.,  1910,  712-717. 
Chalmers,  (A.J.) 

See  Castellani,  (A.) 
Christy,  (C.) 

11.  Ornithodorus  Mouhata  and  tick  fever  in  man.   Br.  M.  J.,  Lond.,  1903, 

II,  652-653. 
Chowning,  (W.  M.) 

12.  Studies   in    Rocky    Mountain   spotted   fever.     J.    Minn.    M.    Ass., 

Minneap.,  1908,  XXVII,  45-49. 
See  also  Wilson,  (L.  B.) 
Cobb,  (J.  O.) 

13.  The  so-called  "spotted  fever"  of  the  Rocky  Mountains.     A  New 

Disease  in  the  Bitter  Root  Valley,  Montana.     Pub.  Health  Rep., 
U.   S.    Pub.    Health   and   Mar.-Hosp.    Serv.,   Wash.,    1902,   XVII, 
1866-1870. 
COOLEY,  (R.A.) 

14.  Preliminary  report  on  the  wood  tick.    Bull.  75,  Montana  Experiment 

Station,  Bozeman,  Mont.,  1908. 
iS.  Tick  Control  in  relation  to  the  Rocky  Mountain  spotted  fever.    Bull. 
85,  Montana  Experiment  Station,  Bozeman,  Montana,  1911. 
Craig,  (C.  F.) 

16.  The  relation  of  the  so-called  "Piroplasma  Hominis"  and  certain  de- 

generative changes  in  the  erythrocytes.     Am.  Med.,  Phila.,   1904, 
VIII,  1016-1017. 
See  also  Ashburn,  (P.M.) 
Davis,  (B.  F.) 

17.  Unfinished  experiments  of  Dr.  Howard  T.  Ricketts  on  Rocky  Moun- 

tain spotted  fever.      Cotitrib.  to   Med.   Science,  Univ.   of  Chicago 
Press,  Chicago,  191 1,  409-418. 
Davis,  (B.  F.)  and  Peterson,  (W.  F.) 

18.  Complement   deviation   in  Rocky   Mountain  spotted  fever.      Jour. 

Infect.  Dis.,  191 1,  VIII,  330-338. 


ROCKY  MOUNTAIN  SPOTTED  FBVBR.  25 

See  also  Contrib.  to  Med.  Science,  Ricketts,  Univ.  of  Chicago  Press, 
191 1,  419-427. 
Geary,  (J.  W.) 

19.  A  case  of  spotted  fever.    Med.  Sentinel,  Portland,  Oreg.,  1905,  XIV, 

GOLDBERGER,  (J.) 

See  Anderson,  (J,  F.) 
Gomez,  (L.) 

20.  Rocky  Mountain  spotted  fever  in  the  rabbit.     J.  Infect.  Dis.,  Chi- 

cago, 1909,  VI,  382-386. 
See  also  Ricketts,  (H.T.) 

GWINN,  (R.) 

21.  The  so-called  "spotted  fever."     The  Missoulian,  Missoula,  Mont., 

1902. 
Heinemann,  (R.  G.)  and  Moore,  (J.J.) 

22.  The  production  and  concentration  of  a  serum  for  Rocky  Mountain 

spotted  fever.   J.  Am.  Med.  Ass.,  Chicago,  191 1,  LVII,  198. 
Henshaw,  (H.  W.)  andBiRDSEYE,  (C.) 

23.  The  mammals  of  the  Bitter  Root  Valley,  Montana,  in  their  relation 

to  spotted  fever.    U.  S.  Dept.  Agric,  Bur.  Biolog.  Surv.,  Circ.  No. 
82,  Wash.,  Govt.  Print.  Office,  191 1. 
HiGGS,  (De  W.  p.) 

24.  Rocky  Mountain  fever.    Chicago  Med.  Times,  1908,  XL,I,  272-274. 
Hunter,  (W.  D.)  and  Bishopp,  (F.  C.) 

25.  Some  of  the  more  important  ticks  of  the  United  States.    Yearbook, 

U.  S.  Dept.  Agric.  for  1910,  Wash.,  Govt.  Print.  Office,  191 1. 
Kieffer,  (C.  F.) 

26.  Intermittent  tick  fever.    Preliminary  report  on  a  new  type  of  fever 

due  to  tick  bite    (ixodiasis).     J.  Am.  Med.  Ass.,  Chicago,   1907, 
XLVIII,  1154-1158. 
King,  (W.  W.) 

27.  Bxperimental   transmission   of  Rocky  Mountain  spotted  fever  by 

means  of  the  tick.   Preliminary  note.    Pub.  Health  Rep.,  U.  S.  Pub. 
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XXI,  863-864. 
Le  Count,  (E.  R.) 

28.  A   contribution   to   the  pathological  anatomy   of  Rocky   Mountain 

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Contributions  to  Med.  Science,  Ricketts,  Univ.  Chicago  Press,  1911, 
445-450. 
Marsden,  (W.  L.) 

29.  Spotted  fever  in  Oregon.    Med.  Sentinel,  Portland,  Oreg.,  1903,  XI, 

389. 
Maver,  (M.  B.) 

30.  Transmision  of  spotted  fever  by  the  tick  in  nature.   J.  Infect.  Dis., 

Chicago,  191 1,  VIII,  322-324.     See  also  Contrib.  to  Med.  Science, 
Ricketts,  Univ.  Chicago  Press,  191 1,  437-439. 

31.  Transmission  of  spotted  fever  by  other  than  Montana  and  Idaho 


26  P.  A.  SURGEON  W.  C.  RUCKBR. 

ticks.    J.  Infect.  Dis.,  191 1,  VIII,  327-331.     See  also  Contribut.  to 
Med.  Science,  Ricketts,  Univ.  Chicago  Press,  191 1,  440-444. 
Maxey,  (E.  E.) 

32.  Some  observations  on  the  so-called  "spotted  fever"  of  Idaho.    Med. 

Sentinel,  Portland,  Oreg.,  1899,  VII,  433-438. 

33.  Rocky    Mountain    spotted     {tick)     fever,    with    special    reference 

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1906,  XIV,  370. 
McCalla,  (L.  p.) 

35.  Direct  transmission  from  man  to  man  of  Rocky  Mountain  spotted 

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MCCULLOUGH,  (G.  T.) 

36.  Spotted  fever.    Med.  Sentinel,  Portland,  Oreg.,  1902,  X,  225-228. 
Milne,  (A.  D.) 

See  Ross. 
Moore,  (J.  J.) 
See  Heinemann. 

2,7-  Time  relationships  of  the  wood  tick  in  the  transmission  of  Rocky 
Mountain  spotted  fever.    J.  Inf.  Dis.,  191 1,  VIII,  339-350.    See  also 
Contrib.  to  Med.  Science,  Ricketts,  Univ.  Chicago  Press,  191 1,  428- 
436. 
MoosER,  (C.  E.) 

38.  Rocky  Mountain  spotted  fever.     J.  Am.  Med.  Ass.,  Chicago,  1906, 

XLVII,  686. 
OsLER,  (W.) 

39.  Rocky  Mountain  spotted  fever.    Mod.  Med.,  Lea  Bros.  &  Co.,  N.  Y., 

1907,  III,  535-540. 
Pearce,  (R.  a.) 

40.  Tick  or  Rocky  Mountain  spotted  fever.     Utah  M.  J.,  (Denver  M. 

Times),  1908-9,  XXVIII,  415. 
Peterson,  (W.  F.) 

See  Davis. 
Ricketts,  (H.  T.) 

41.  The  Study  of  Rocky  Mountain  spotted  fever  by  means  of  animal 

inoculations.  J.  Am.  Med.  Ass.,  Chicago,  1906,  XLVII,  33-36,  and 
Contrib.  to  M.  Science,  Ricketts,  Univ.  Chicago  Press,  1911,  278-287. 

42.  The  transmission  of  Rocky  Mountain  spotted  fever  by  the  bite  of  the 

wood  tick.  J.  Am.  Med.  Ass.,  Chicago,  1906,  XLVII,  358.  See  also 
Contrib.  to  Med.  Science,  Ricketts,  Univ.  Chicago  Press.,  191 1, 
287-290. 

43.  Further  observations  on  Rocky  Mountain  spotted  fever  and  Derma- 

centor  occidentalis.  J.  Am.  Med.  Ass.,  Chicago,  1906,  XLVII,  1067- 
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Press,  191 1,  291-298. 


ROCKY  MOUNTAIN  SPOTTED  FEVER.  27 

44.  Observations   on   the  virus  and   vieans   of   transmission   of  Rocky 

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45.  The   role   of   the   wood-tick    {Derviacentor   occideiitalis)    in   Rocky 

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46.  Further  experiments  with  the  wood-tick  in  relation  to  Rocky  Moun- 

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47.  Demonstration  of  a  micro-organism  which  apparently  has  a  specific 

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48.  A  summary  of  investigations  of  the  nature  and  means  of  transmis- 

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50.  General  report  of  an  investigation  of  Rocky  Mountain  spotted  fever, 

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53.  A   micro-organism  which  apparently  has  a  specific  relationship   to 

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54.  Studies  on  immunity  in  Rocky  Mountain  spotted  fever.    J.  Inf.  Dis., 

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28  P.  A.  SURGEON  n\  C.  KUCKUR. 

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60.  The  infinite  torment  of  flies.     Med.  Rev.,  St.  Louis,   1905,  XXIII, 

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62.  Mountain  or  spotted  fever,  as  seen  in  Idaho  and  eastern  Oregon, 

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66.  A  zoological  investigation  into  the  cause,  transmission,  and  source 

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ROCKY  MOUNTAIN  SPOTTED  FEVER.  29 

TUTTLE,  (T.  D.) 

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Army,  1896,  Wash.,  Govt.  Print.  Office,  1896,  60-65, 


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APR    26  1937 


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THE  UNIVERSITY  OF  CALIFORNIA  UBRARY 

